the moment of disaster . can be anything, an earthquake , a volcano, a flood, a twister, a giant laser beam coming from the sky, a tsunami showing and indicating the power of nature over humanity. begining of destruction. I have seen devastated environment illustrations but not many dynamic disaster moment illustrations.

how about myth gods in a specific era ?
from china to europe every culture have their own myth gods .
how would they look if they appeared in the early 19ths ?
it can be another era or specific timezone. just to give an example, it can be;
post nuclear war steam punk venus.
second world war thor.

this may sound odd but , fantasy characters sports.
I would love to illustrate an orc playing basketball in middle earth.
a dark elf in his armor playing hockey on a frozen lake next to an elf village.
or they may have their own sports like tree knocking contest for dwarves? I dont know. they can be in our daily environments too. a streetball ogre?

I agree with Suirebit. By giving a slightly abstract theme, all different disciplines can compete and throw in their own ideas. The last few contests have been very character based, and I know a lot of us enviro guys have been waiting on a contest like this months